Most fire protection systems operate at positive pressure or at atmospheric pressure. So called “dry systems” or “dry pipe systems” operate through a network of fluid lines or pipes, filled with a gas (typically air—but other gases can be used). A monitoring system detects any pressure drops in the system to identify either a gas leak in the pipes or the opening of one or more sprinklers. When a sprinkler opens, the pressure in the pipes decreases and the pressure sensors detect the resulting pressure drop. Depending on the pressure drop rate detected, a compressor can be activated to re-pressurize the pipes (in case of a leak), or a water valve can be opened to let water flow through the pipe network (in case of a fire/sprinkler opening).
Since dry systems pipes are filled with fluid, when a sprinkler is activated, the gas fluid flow must escape or be expelled from the open sprinkler head before the water can reach the sprinkler head and be delivered to the specific hazard. The volume of gas fluid which must be vented, limits the use of grid piping network configurations. Furthermore, most of these systems use air, which contains moisture, as fluid gas, and as such may cause corrosion in the piping network.
An example of such system is described in U.S. Pat. No. 5,971,080, filed by Central Sprinkler Corporation, and now owned by Tyco Fire Products LP. This system monitors and detects a rate of loss of pressure (negative rate of change) in gas charged fluid flow lines. This system is designed for dry pipe systems charged with fluid at a pressure maintained above atmospheric pressure.
Also known in the art, is a virtual accelerator, such as described in U.S. Pat. No. 6,357,531, that detects a sprinkler head activation but only in charged fluid flow lines at a pressure maintained above atmospheric pressure.
In view of the above, there is a need for a device and a method for detection of a sprinkler opening for piping networks maintained under vacuum pressure which would be able to overcome or at least minimize some of the above-discussed prior art concerns.